The Delaware Aqueduct Repair Project and its Impacts on Watershed Communities

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DEP is implementing a project to repair the longest tunnel in the world—the Delaware Aqueduct. We will be connecting a newly constructed 2.5-mile bypass tunnel to structurally sound portions of the existing Delaware Aqueduct, permanently conveying water around a leak. To make this connection, we had anticipated shutting down the Delaware system for eight months, starting in October 2024. However, the lack of rain upstate this fall has required DEP to halt repairs to the Delaware Aqueduct until 2025.

The Delaware Aqueduct begins at Rondout Reservoir in Ulster County and conveys about 50 percent of New York City’s drinking water every day. This repair project, as well as water supply operations throughout the shutdown, have been in the planning process for more than 20 years and will have impacts on the supply system’s reservoir levels as well as some recreation activities in the City’s watersheds.

To learn about New York City’s water supply systems, visit Water Supply. For up-to-date reservoir levels and release rates, visit Reservoir Levels.

Shutdown Timeline

The start of the shutdown is being carefully timed to coincide with the end of peak summer demand on the water system. An unusually dry and hot summer before the planned shutdown—such as occurred in 2022—could delay the project. Unforeseen complications and computer modeling that predicts reservoir refill probabilities will drive all “go-no-go” decisions leading into and throughout the shutdown. Lack of precipitation in Fall of 2024 has made it necessary to postpone the shutdown until 2025. For real-time updates and outreach event information, please follow our NYC Watershed Facebook page.

Over the past decade, we have worked on several projects to ensure New York City will have a reliable supply of drinking water during the shutdown period: see Final Concrete Lining on Bypass Tunnel Completed, Final Steel Segment Lowered into Bypass Tunnel, Catskill Aqueduct Rehabilitation, and Bypass Tunnel Excavation Complete for more details.

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Impacts on the Delaware System

The Delaware system, which includes Cannonsville, Pepacton, Neversink, and Rondout reservoirs in Sullivan, Ulster, and Delaware counties, will be shut down prior to the final bypass connection. The shutdown had been planned for October 2024 but drought-like conditions necessitated postponing this phase of the project until Fall of 2025. Rondout Reservoir serves as the central collecting reservoir for the three other Delaware system reservoirs, but during the shutdown, it will only receive water from its 95-square-mile watershed. In preparation for the shutdown, we installed three siphons as an extra method to remove water from Rondout Reservoir, which will help manage surface water levels and reduce the likelihood that water will pass through its spillway.

Prior to the shutdown period, all four Delaware system reservoirs will be drawn from more than usual. Depending on the amount of precipitation, each reservoir is expected to be drawn down from capacity by 30 percent or more, creating a substantial void that will help to reduce storm impacts in the region. During the shutdown period, Delaware system reservoirs will refill and continue downstream releases into the Delaware River.

The shutdown should not impact public recreational uses of the lands and water bodies of the Delaware System. To monitor recreation updates, visit: Recreation.

For more information, download the Delaware Watershed Factsheet for the Delaware Aqueduct Shutdown.

Impacts on the Catskill System

The Catskill system, comprised mainly of Ashokan and Schoharie reservoirs in Ulster, Delaware, Greene, and Schoharie counties, typically provides about 40 percent of the city’s water supply and will become the primary source of the city’s water supply throughout the shutdown. The Catskill systems near 160-billion-gallon storage capacity west of the Hudson River is expected to be minimized before the October 2025 shutdown of the Delaware Aqueduct, and surface levels of Ashokan will likely appear lower during winter 2025-26 while the Delaware is shutdown. Regulated releases from Ashokan into the Esopus Creek will continue throughout the Delaware shutdown as per the Interim Release Protocol.

The shutdown should not impact public recreational uses of the lands and water bodies of the Catskill System. To monitor recreation updates, visit: Recreation.

For more information, download the Catskill Watershed Factsheet for the Delaware Aqueduct Shutdown.

Impacts in the Croton System

The Croton system is comprised of 12 interconnected reservoirs and three controlled lakes in Westchester and Putnam counties, and typically provides about 10 percent of the city’s water supply. During the shutdown, the system will ramp up to provide 30 percent of the city’s water supply. Several of the reservoirs will be drawn down more substantially than usual, and large pumping stations will be used to push Croton system water into the lower portion of the Delaware Aqueduct, which will remain operational from West Branch Reservoir to Kensico Reservoir and into the city’s distribution system. Water in West Branch and Boyds Corner reservoirs will be held as reserve during the shutdown period.

Boating and Fishing Recreation Impacts

The shutdown should not impact public land recreational use, but boating and fishing activities throughout the Croton system reservoirs in Westchester and Putnam counties are expected to change. Ice fishing will be restricted on several reservoirs during winter 2023/24 and winter 2025/26 and some reduced downstream releases of water to various rivers and streams could inhibit stream fishing in several areas. To monitor boating and fishing recreation updates, visit Boating for Anglers and Fishing.

For more information, download the Croton Watershed Factsheetfor the Delaware Aqueduct Shutdown.